The technique of stereoscopically displaying a subject by using images of the same subject captured from a plurality of points of view has been conventionally developed. In such a case, a density value corresponding to the same portion of the subject may vary from image to image, depending on a difference in conditions at the time of capturing the images, and the like. Therefore, processing is executed to correct a density value of pixels included in one image with respect to a density value of pixels included in the other image. Various conversion functions such as a density value conversion table is used for this correction processing.
The following is known as the prior art related to the aforementioned correction processing.
For example, in a color adjusting apparatus disclosed in Japanese Laid-Open Patent Publication No. 2010-16803 (PTD 1), a captured image represented by an RGB color space of one camera A of two cameras A and B is defined as a reference image Sa, and a captured image represented by an RGB color space of the other camera B is defined as an image to be adjusted Sb. Color space conversion is applied to image to be adjusted Sb by a color adjusting unit in the color adjusting apparatus, and cumulative histogram matching processing is applied with respect to a component Ha(k) of reference image Sa, for each component after this color space conversion. After this cumulative histogram matching processing, the original RGB space is recovered. An adjusted image Sb′ having the same color tone as that of reference image Sa is thus generated.
According to a method disclosed in “Color Calibration between Two Different Cameras”, Shintaro Inamura, Akira Taguchi (NPD 1), images of the same subject are captured by two cameras arranged side by side, and conversion is made to match a histogram of the image captured by one camera to a histogram of the image captured by the other camera such that cumulative histograms of the obtained two images match with each other. Then, color space conversion is applied, and thereafter, histogram conversion is applied for each component. Thereafter, an RGB color space is recovered by reverse conversion.